I am not sure off-hand exactly what that error code means without delving into the source code. Is there any chance of supplying the calibre2opds log that was associated with that error being generated - that might give some clues?

One thing that has just occurred to me from what some users have encountered in the past! You might want to set the permissions on the calibre2ods install folder to allow your user full access. For some users this has fixed what look like similar problems. I am not at all sure why - I can only assume it is something buried in a Java library somewhere. What is particularily strange is that not all users seem to require this.